1. Field of the Invention
The present invention relates to a method for adjusting the temperature of a printing press and an apparatus therefor, and more specifically to a method for adjusting the temperature of a printing press by which the temperature of inking rollers or printing plate surface is adjusted to suppress the decrease in ink viscosity caused by ink temperature increase during printing, and to an apparatus therefor.
2. Description of the Related Art
During the operation of printing presses, the temperature of inking rollers or printing plate surface gradually increases and ink viscosity decreases under the effect of friction heat or the like. As a result, a variety of adverse effects are produced on printing quality. Those effects are especially significant in waterless offset printing presses, where the viscosity of ink decreases, the repellency drops, and the so called xe2x80x9cscummingxe2x80x9d appears in non-image areas owing to temperature increase. For this reason, various methods and apparatuses for adjusting the temperature of printing presses for the purpose of preventing temperature increase in inking arrangements and printing plate surfaces have been suggested for the usual offset presses.
Conventional cooling apparatuses for inking arrangements typically suppress the increase in temperature of rollers by passing cooling water inside base rollers or vibrator rollers of inking arrangements (for example, Publications of Japanese Patent Application No. H8-29550, H6-344538 and so on). Direct blowing of cooling air on a printing plate surface was also suggested as a method for cooling the printing plate surface (for example, Japanese Patent No. 2572516, Publication of Japanese Patent Application H1-72846 and so on).
However, in the conventional cooling apparatuses for inking arrangements, it was difficult to control the temperature of a roller group constituting the inking arrangement, so as to maintain separately the optimum temperature of each roller according to the function thereof, and a cooling apparatus demonstrating a satisfactory temperature adjustment function has not yet been developed. Furthermore, in case of printing presses in which a plurality of inking arrangements are disposed around one blanket wheel and multicolor printing is conducted on a cylindrical body, all inking arrangements have different degrees of temperature increase owing to the difference in the ink build-up depending on the design of each color or because of the difference in setting state between the inking arrangements (for example, lubrication state in bearing units). However, in prior art, the temperature adjustment of inking rollers for each inking arrangement has not been conducted based on the increase in temperature of each inking arrangement. Furthermore, a problem associated with the method of blowing cooling air onto a printing plate surface for cooling thereof is that transfer defects caused by ink drying on the printing plate surface can easily occur. Thus, the problem is that the conventional methods for adjusting the temperature of printing presses have not yet provided a satisfactory temperature adjustment function, and in the waterless offset printing presses requiring an especially sensitive temperature adjustment, a scumming effect caused by the decrease in repulsiveness in non-image areas could easily occur. Waterless lithographic printing was recently tested as a method for printing on cans to meet the demand for diversified printing patterns on cylindrical cans. However, technological problems requiring resolution, such as a decrease in yield caused by the above-described scumming effect, were encountered.
The present invention is aimed at the resolution of the above-described problems, and it is an object of the present invention to provide a method and apparatus for adjusting the temperature of a printing press that can provide for reliable temperature adjustment of the printing press, can be used to adjust the temperature according to the temperature increase of inking arrangements of each color in case of multicolor printing, generate no transfer defects caused by ink drying, even in temperature adjustment of printing plates, allow for optimum cooling, and make it possible to obtain good printing quality, without scumming even in waterless lithographic printing.
The method for adjusting the temperature of a printing press in accordance with the present invention, which resolves the above-described problems is a method for adjusting the temperature of a printing press in which the temperature is adjusted by passing a temperature-adjusting water to the shaft portion of rollers of inking arrangements, wherein the roller groups of inking arrangements are divided into a first system in which the temperature of rollers with an ink feed function is adjusted and a second system in which the temperature of rollers with an ink distribution function is adjusted and temperature adjustment can be conducted separately for the first system and second system. Passing the temperature-adjusting water is not necessarily conducted to all of the rollers constituting the rollers with an ink feed function and rollers with an ink distribution function. Thus, the water may be supplied to a fountain roller and a transfer roller of the rollers with an ink feed function and to three vibrator rollers of the rollers with an ink distribution function. Further, in the first system, the temperature of the rollers with an ink feed function by virtue of adjusting the water temperature at a constant flow rate of temperature-adjusting water passing through the shaft portion of the rollers is preferably adjusted, and in the second system, the temperature of rollers with an ink distribution function is preferably adjusted by virtue of adjusting the water temperature for a constant value for each operation state and also by adjusting the water flow rate for each inking arrangement.
The present invention can be applied to a printing press for multicolor printing on cylindrical bodies, in which a plurality of inking arrangements are disposed around one blanket wheel. In such a case, the inking arrangements of each color are preferably controlled with one temperature adjustment apparatus, and in the second system, the temperature preferably can be adjusted for each inking arrangement of each color.
With another method for adjusting the temperature of a printing press in accordance with the present invention, the plate cylinder is cooled by blowing cooling air in the axial direction of the plate cylinder from the axial extension of the plate cylinder. Further, the temperature adjustment of a printing press can be conducted more effectively by employing together the method for cooling the rollers of the first system and second system of the color inking arrangements and the method for cooling the plate cylinder by blowing cooling air in the axial direction of the plate cylinder. The above-described methods can be effectively applied to waterless offset printing presses.
In the apparatus for adjusting the temperature of a printing press in accordance with the present invention, the conduit for passing the temperature-adjusting water to a roller group in an inking arrangement is divided into a first system conduit for adjusting the temperature of rollers with an ink feed function and a second system conduit for adjusting the temperature of rollers with an ink distribution function, pumps and heaters are provided separately for the first system conduit and second system conduit, and the first system conduit and second system conduit have an apparatus for roller temperature adjustment in an inking arrangement which is capable of separate temperature adjustment.
In the above-mentioned first system conduit and second system conduit, the pumps, heaters, and valves for adjusting the amount of supplied cooling water from the cooling water source which are used commonly for inking arrangements of all colors are provided in respective supply-side conduit of the first system integrated conduit and second system integrated conduit that are integrated with the first system conduit and second system conduit having the upstream sides thereof enclosed inside one temperature adjustment unit, and the respective temperatures of temperature-adjusting water can be controlled by one temperature adjustment unit according to the operation state. Furthermore, a flow rate adjustment valve is provided for each second system conduit of the inking arrangements of each color branched from the second system integrated conduit, the amount of water passed to the rollers of the second system are controlled for the inking arrangements of each color and the roller temperature in the second system can be controlled for each color inking arrangement.
Another apparatus for adjusting the temperature of a printing press in accordance with the present invention is an apparatus for adjusting the temperature of a printing press for multicolor printing on cylindrical bodies, in which a plurality of inking arrangements are disposed around one blanket wheel, this apparatus comprising a plate cylinder shaft forced air cooling unit in which a chamber is provided opposite a side surface of the blanket wheel on the axial direction side thereof, air cooling ducts are provided which extend from the chamber toward the center of the plate cylinder center of each color, and air cooling openings for blowing cooling air toward the plate cylinder shaft are provided at the ends of the air cooling ducts.
The air cooling ducts are preferably provided so that they can be shifted to a position in which they place no obstacle during setup or adjustment of the plate cylinder and to a position in which the air cooling openings face the plate cylinder axis during printing. Providing the apparatus for adjusting the temperature of inking arrangements and the plate cylinder shaft forced air control apparatus makes it possible to obtain the temperature adjustment apparatus with even better temperature adjustment effect. Utilizing such a waterless offset printing press, in particular, for waterless lithographic printing on cans makes it possible to suppress the appearance of scumming and to increase printing quality in waterless lithographic printing on cans.